Electrochemical biosensors are well known and have been used to determine the concentration of various analytes from biological samples, particularly from blood. Examples of such electrochemical biosensors are described in U.S. Pat. Nos. 5,413,690; 5,762,770 and 5,798,031; and 6,129,823 each of which is hereby incorporated by reference.
It is desirable for electrochemical biosensors to be able to analyze analytes using as small a sample as possible, and therefore it is necessary to minimize the size its parts, including the electrodes, as much as possible. As discussed below, screen-printing, laser scribing, and photolithography techniques have been used to form miniaturized electrodes.
Electrodes formed by screen-printing techniques are formed from compositions that are both electrically conductive and which are screen-printable. Furthermore, screen printing is a wet chemical technique that generally allows for the reliable formation of structures and patterns having a gap width or feature size of approximately 75 μm or greater. Such techniques are well known to those of ordinary skill in the art.
Laser scribing is a technique that usually uses a high power excimer laser, such as a krypton-fluoride excimer laser with an illumination wavelength of 248 nm, to etch or scribe individual lines in the conductive surface material and to provide insulating gaps between residual conductive material which forms electrodes and other desired components. This scribing is accomplished by moving the laser beam across the surface to be ablated. The scribing beam generally has a relatively small, focused size and shape, which is smaller than the features desired for the product, and the formation of the product therefore requires rastering techniques. It is therefore appreciated that such a technique can be rather time consuming if a complex electrode pattern is to be formed on the surface. Still further, it is appreciated that the precision of the resulting edge is rather limited. This scribing technique has been used to ablate metals, polymers, and biological material. Such systems are well known to those of ordinary skill in the art, and are described in U.S. Pat. Nos. 5,287,451, 6,004,441, 6,258,229, 6,309,526, WO 00/73785, WO 00/73788, WO 01/36953, WO 01/75438, and EP 1 152 239 each of which is hereby incorporated by reference. It would be desirable to have a new method of forming electrodes which allows precise electrode edges, a variety of feature sizes, and which can be formed in a high speed/throughput fashion without the use of rastering.
According to the present invention a method of making a biosensor electrode pattern is provided. The method comprises the steps of providing an electrically conductive material on a base and forming electrode patterns on the base using broad field laser ablation. In one aspect at least two electrode patterns are formed on the base that have different feature sizes.
According to the present invention a method of making a biosensor is provided. The method comprises the steps of providing an electrically conductive material on a base and partially removing the conductive material from the base using laser ablation so that less than 90% of the conductive material remains on the base and at least one electrode pattern is formed from the conductive material. In one aspect, at least one electrode pattern has an edge extending between two points, a standard deviation of the edge from a line extending between two points being less than about 6 μm along the length of the edge.
According to the present invention a method of making a biosensor is provided. The method comprises the steps of providing an electrically conductive material on a base, forming electrode patterns on the base using broad field laser ablation, wherein at least two electrode patterns have different feature sizes, and extending a cover over the base. In one aspect, the cover and base cooperate to define a sample-receiving chamber and at least a portion of the electrode patterns are positioned in the sample-receiving chamber.
According to the present invention a method of making a biosensor electrode set is provided. The method comprises providing a laser system having a lens and a mask, and ablating through a portion of a first metallic layer with a laser, to form an electrode pattern, the pattern of ablation being controlled by the lens and the mask. In one aspect, the metallic layer is on an insulating base.
According to another aspect of the present invention, a method of making a biosensor strip is provided. The method comprises providing a laser system having at least a laser source and a mask, and forming an electrode set by ablating through a portion of a metallic layer with a laser, a pattern of ablation being controlled by the mask, wherein said metallic layer is on an insulating base.
Still further, according to the present invention a method of making a biosensor is provided. The method comprises providing an electrically conductive material on a base and forming a pre-determined electrode pattern on the base using laser ablation through a mask, the mask having a mask field with at least one opaque region and at least one window formed to allow a laser beam to pass through the mask and to impact predetermined areas of the electrically conductive material.
According to the present invention a method of making a biosensor electrode set is provided. The method comprises providing a laser system having a lens and a mask, ablating through a portion of a metallic layer with a laser, to form an electrode pattern, the pattern of ablation being controlled by the lens and the mask, wherein said first metallic layer is on an insulating substrate.
According to the present invention a method of making an electrode set ribbon is provided. The method comprises providing a laser system having a lens and a mask and ablating through a portion of a metallic layer with a laser, to form a plurality of electrode patterns. The pattern of ablation is controlled by the lens and the mask, the metallic layer is on an insulating substrate, and the electrode set ribbon comprises a plurality of electrode sets.
Still further according to the present invention a method of making a sensor strip is provided. The method comprises providing a laser system having a lens and a mask, forming an electrode set by ablating through a portion of a first metallic layer with a laser, and cutting said substrate, to form a strip. A pattern of ablation is controlled by the lens and the mask and the first metallic layer is on an insulating substrate.
The following definitions are used throughout the specification and claims:
As used herein, the phrase “electrically conductive material” refers to a layer made of a material that is a conductor of electricity, non-limiting examples of which include a pure metal or alloys.
As used herein, the phrase “electrically insulative material” refers to a material that is a nonconductor of electricity.
As used herein, the term “electrode” means a conductor that collects or emits electric charge and controls the movement of electrons. An electrode may include one or more elements attached to a common electrical trace and/or contact pad.
As used herein, the term “electrical component” means a constituent part of the biosensor that has electrical functionality.
As used herein, the phrase “electrode system” refers to an electrical component including at least one electrode, electrical traces and contacts that connect the element with a measuring instrument.
As used herein, the phrase “electrode set” is a grouping of at least two electrodes that cooperate with one another to measure the biosensor response.
As used herein, the term “pattern” means a design of one or more intentionally formed gaps, a non-limiting example of which is a single linear gap having a constant width. Not included in the term “pattern” are natural, unintentional defects.
As used herein, the phrase “insulative pattern” means a design of one or more intentionally formed gaps positioned within or between electrically insulative material(s). It is appreciated that electrically conductive material may form the one or more gaps.
As used herein, the phrase “conductive pattern” means a design of one or more intentionally formed gaps positioned within or between electrically conductive material(s). It is appreciated that exposed electrically insulative material may form the one or more gaps.
As used herein, the phrase “microelectrode array” means a group of microelectrodes having a predominantly spherical difusional characteristic.
As used herein, the phrase “macroelectrode array” means a group of macroelectrodes having a predominantly radial diffusional characteristic.
As used herein, the phrase “electrode pattern” means the relative configuration of the intentionally formed gaps situated between the elements of electrodes in an electrode set. Non-limiting examples of “electrode patterns” include any configuration of microelectrode arrays and macroelectrode arrays that are used to measure biosensor response.
As used herein, the phrase “feature size” is the smallest dimension of gaps or spaces found in a pattern. For example, in an insulative pattern, the feature size is the smallest dimension of electrically conductive gaps found within or between the electrically insulative material(s). When, however, the pattern is a conductive pattern, the feature size is the smallest dimension of electrically insulative gaps found within or between the electrically conductive material(s). Therefore, in a conductive pattern the feature size represents the shortest distance between the corresponding edges of adjacent elements.
As used herein, the term “interlaced” means an electrode pattern wherein the elements of the electrodes are interwoven relative to one another. In a particular embodiment, interlaced electrode patterns include electrodes having elements, which are interdigitated with one another. In the simplest form, interlaced elements include a first electrode having a pair of elements and a second electrode having a single element received within the pair of elements of the first electrode.
As used herein, the term “ablating” means the removing of material. The term “ablating” is not intended to encompass and is distinguished from loosening, weakening or partially removing the material.
As used herein, the phrase “broad field laser ablation” means the removal of material from a substrate using a laser having a laser beam with a dimension that is greater than the feature size of the formed pattern. Broad field ablation includes the use of a mask, pattern or other device intermediate a laser source and a substrate, which defines a pattern in which portions of the laser beam impinge on the substrate to create variable and multiple patterns on the substrate. Broad field laser ablation simultaneously creates the pattern over a significant area of the substrate. The use of broad field laser ablation avoids the need for rastering or other similar techniques that scribe or otherwise define the pattern by continuous movement of a relatively focused laser beam relative to the substrate. A non-limiting example of a process for broad field laser ablation is described below with reference to biosensor 210.
As used herein, the term “line” means a geometric figure formed by a point moving in a first direction along a pre-determined linear or curved path and in a reverse direction along the same path. In the present context, an electrode pattern includes various elements having edges that are defined by lines forming the perimeters of the conductive material. Such lines demarcating the edges have desired shapes, and it is a feature of the present invention that the smoothness of these edges is very high compared to the desired shape.
As used herein, the term “point” means a dimensionless geometric object having no properties except location.
As used herein, the term “smooth” means an edge of a surface deviating from a line extending between two points not more than about 6 μm. Further, for patterns having a feature size of about 5 μm or less, “smooth” means an edge of a surface deviating from a line extending between two points less than one half the feature size of the conductive pattern. For example, such lines demarcate the edges that have desired shapes, and the smoothness of these edges is very high compared to the desired shape.
As used herein, the phrase “biological fluid” includes any bodily fluid in which the analyte can be measured, for example, interstitial fluid, dermal fluid, sweat, tears, urine, amniotic fluid, spinal fluid and blood.
As used herein, the term “blood” includes whole blood and its cell-free components, namely plasma and serum.
As used herein, the term “working electrode” is an electrode at which analyte, or product, is electrooxidized or electroreduced with or without the agency of a redox mediator.
As used herein, the term “counter electrode” refers to an electrode that is paired with the working electrode and through which passes an electrochemical current equal in magnitude and opposite in sign to the current passed through the working electrode. The term “counter electrode” is meant to include counter electrodes, which also function as reference electrodes (i.e., a counter/reference or auxiliary electrode).
As used herein, the term “electrochemical biosensor” means a device configured to detect the presence and/or measure the concentration of an analyte by way of electrochemical oxidation and reduction reactions within the biosensor. These reactions are transduced to an electrical signal that can be correlated to an amount or concentration of the analyte.
Additional features of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiment exemplifying the best mode known for carrying out the invention. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.